Machine for manufacturing heat exchanger tube

ABSTRACT

Apparatus is disclosed for forming heat exchanger tubes having two helically wound foil strips each of which is provided with two lanced legs extending substantially perpendicular to the base tube. The foil stock is supplied from the interior of a coil consisting of two interleaved strips wound in a spiral form. The strips are separately fed and formed and are subsequently wound on an axially movable non-rotating tube. The winding head subassemblies are symmetrically positioned to provide dynamic balancing.

145! Sept.5,1972

United States Patent Venables, III

3,134,166 5/1964 Venables ...........29/l57.3 AH 3,160,129 12/1964Venables.................29/202D Primary Examiner-Thomas H. EagerAttorney-Harry B. O'Donnell, 111 et a1.

Herbert J. Venables, 111, Cleveland, Ohio [22] Filed: July 13, 1970ABSTRACT Apparatus is disclosed for forming heat exchanger App1.No.:54,304

tubes having two helically wound foil strips each of 'i 2: which isprovided with two lanced 1egs extending sub- 1573 Manually perpendicularto the base tube. The foil [58] Field of Seareh....l13/1;

stock is supplied from the interior of a coil consisting of twointerleaved strips wound in a spiral form. The strips are separately fedand formed and are sub- [56] References Cited UNITED STATES PATENTSsequently wound on an axially movable non-rotating tube. The windinghead subassemblies are symmetrically positioned to provide dynamicbalancing.

3,005,253 10/1961 Venables ...........29/157.3 AH

8 Claims, 14 Drawing figures P'A'IENTEBsEP' m: 3.688.375

SHEEY 3 BF 5 INVENTOR.

BY Mq/euwf Anne/M67044 A542: #4020041 1477 walls):

PATENTED E 5 i9 SHEET t [If 5 MACHINE FOR MANUFACTURING HEAT EXCHANGERTUBE BACKGROUND OF THE INVENTION This invention relates generally to themanufacture of heat exchanger tubes and more particularly to a novel andimproved method and apparatus for forming such tubes and to a novel andimproved heat exchanger tube produced by such method and apparatus.

PRIOR ART The present invention is an improvement of the inventionsdisclosed in my prior U.S. Pats; No. 3,005,253 of Oct. 24, 1961; No.3,134,166 of May 26, 1964; and No. 3,160,129 of Dec. 8, 1964. Each ofthese prior patents relates to the manufacture of heat exchanger tubesin which the tube is helically wound with a strip of metal foil stock soas to provide a large external heat exchange surface for the efficientheat transfer through the tube wall. Although such tubing finds itsgreatest use in heaters and air conditioners, it may be used in manyother types of equipment where efficient heat exchange is required.

SUMMARY OF THE INVENTION The apparatus for forming heat exchanger tubingin accordance with the present invention involves means for thesimultaneous winding of a tube with more than one continuous strip ofmetal foil from a rotating winding head. In the illustrated embodiment,two strips engage the tube at tangentially and diametrically oppositepoints of the tube and are simultaneously wound on the tube with adouble helix, so that each turn of the winding head produces twice thelength of wound tubing when compared to the prior machines of my patentsreferred to above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the windinghead of a preferred embodiment of this invention;

FIG. 2 is a plan view of the gear train drive for the various formingand feeding subsystems of the winding head;

FIG. 3 is a fragmentary broken section taken along 3-3 of FIG. 1;

FIG. 4 is a fragmentary section illustrating the foil lancing station;

FIG. 4a illustrates a strip after lancing;

FIG. 5 is an enlarged fragmentary section of one of the stations atwhich the foil is initially formed to a U- shape;

FIG. 6 is an enlarged fragmentary section illustrating the structure ofone of the hemming stations;

FIG. 6a is an enlarged fragmentary section illustrating the formingoperation which occurs at the throat of the hemming station;

FIG. 7 is an enlarged fragmentary section of one form of a novel andimproved tube in accordance with this invention;

FIG. 7a is an enlarged fragmentary section of another form of a noveland improved tube in accordance with this invention; and

FIGS. 8-11 are schematic views progressively illustrating the manner inwhich the coils of foil stock are unwound as the machine operates.

DETAILED DESCRIPTION OF THE DRAWINGS My prior US. Pat. No. 3, l 34,166discloses a winding machine for the manufacture of heat exchanger tubingin which the tubing is fed up through the machine along the center of awinding head. Such machine is provided with feed rollers which operateto straighten the tubing and to insure that the tubing is circular insection. In such prior machine a single strip of foil stock is fed intothe winding head and is lanced along opposite lateral extremities. Thelanced foil strip is then formed to a U- shape and is subsequentlyhemmed to provide a base having a lateral width greater than the spacingbetween the lanced legs. The formed strip is then wrapped around thetubing in a single helix.

The method and apparatus in accordance with the present invention alsoutilizes strips which are first lanced, are subsequently formed to aU-shape, and are thereafter hemmed to the shape substantially asillustrated in such patent. However, the illustrated apparatus inaccordance with the present invention is supplied with a coil consistingof two interleaved spiral strips of stock and the two strips aresimultaneously formed and simultaneously wound onto the tube with adouble helix rather than the single helix of such patent.

A number of distinct advantages are obtained with the present inventionwhen compared to my prior machines as will be discussed in detail below.However, reference should be made to all of my prior patents, listedabove, for a clear understanding of the background of the presentinvention and of the various advantages and features realized with theinventions disclosed therein. Therefore, such prior patents are herebyincorporated by reference.

In order to simplify the understanding of this invention only thewinding head is illustrated and discussed in detail. Such winding headis preferably supported on a main frame as illustrated in my prior [15.Pat. No. 3,134,166 and is driven by a lower drive gearing system asdisclosed therein. The drive for feeding the tubing up through thewinding head of such patent need only be modified to increase the rateof tube feeding compared to the rate of rotation of the winding head.For example, when the base width of the strip is the same as the basewidth of the strip formed on such prior machine, the rate of feeding ofthe tube is doubled by appropriate changes in the tube feed gear driveto accommodate the two strips which are simultaneously wound on thetube.

Referring to FIG. 1, the winding head, designated generally as 10, isjoumaled for rotation about a vertical central axis 11. The tube 12 tobe wound is fed vertically upward through a stationary guide 13 alongthe central axis 11. The entire winding head along with a stock supporttable 14 rotate in a counterclockwise direction as viewed in FIG. 1.However, the winding head 10 rotates at a speed slightly slower than therotational velocity of the table 14. The tube 12 moves only in avertical direction and does not rotate.

Two separate but continuous strips of foil stock 16 and 17 indicatedschematically by dotted lines, feed into diametrically opposite sides ofthe winding head 10. The manner in which the supply coil is wound toprovide two separate strips and the manner in which the strips move fromthe supply coil into the head is discussed in detail below.

Each of the strips 16 and 17 moves along a separate path to the tube 12.However, the two paths are similar and are symmetrically arranged withrespect to the central axis 11. Since the two paths are similar, onlyone will be discussed in detail with the understanding that the detaileddescription applies equally to both paths. The strip 16 enters thewinding head by passing around a guide roller 18 at the periphery of thewinding head. The strip then extends past a guide 19, a pair of guiderolls 21 and 22, and along a guide 23 to a lancing station 24 which islocated substantially adjacent to the central axis 11. The structure ofthe elements forming the lancing station and the operation of lancing isdiscussed in detail below.

From the lancing station 24 the lanced strips 160 then passes to a firstforming station 26 where the lanced strip 160 is bent to a generallyU-shaped configuration. From the first forming station 26 the U- shapedstrip 16b passes to a hemming station 27 wherein the strip is furtherformed to provide a hem at the edges of the base of the strip. From thehemming station 27 the hemmed strip 160 passes around an inclined guideroll 28 which positions the hemmed strip for winding around the tube 12.

Because of the composite movement resulting from the rotation of thewinding head in a plane perpendicular to the axis 11 and the axialmovement of the tube along the axis 11, the hemmed strip is wound aroundthe tube in a helical manner wherein the lead of the helix is equal tothe amount of movement of the tube which occurred during one compieterevolution of the winding head 10. The strip 17 is similarly processedand moves along a similar but opposite path through a lancing station24, a first forming station 26 in which it is formed to a U-shape, and ahemming station 27. From the hemming station 27 associated with thestrip 17 the hemmed strip 17c passes around an inclined guide roller 28and passes to the tube 12 engaging the tube 12 tangentially directlyopposite the engagement of the strip 160 with the tube.

The various elements forming the winding head 10 are symmetricallypositioned with respect to the central axis 11. Therefore, the twolancing stations 24 are located on diametrically opposite sides of theaxis 1 1 an equal distance therefrom. The two forming stations 26 aresimilarly located on diametrically opposite sides of the axis 11 equaldistances therefrom. Similarly, the two hemming stations are equallyspaced and diametrically opposite each other. In each instance thestructure at each forming station is identical to the structure at thecorresponding forming station for the other strip. Therefore, the basicstructure of the winding head provides complete dynamic balancing withrespect to the central axis 11. It should be understood that dynamicbalance is extremely important in such machine since the winding headand the structure associated therewith is relatively large and heavy androtates at a speed in the order of 1,600 rpm or more.

Referring to FIG. 4, the two lancing stations 24 are provided by a drivelancing roll 31 which is joumaled for rotation about the central axis11. Similar idler rolls 32 and 33 are joumaled on the winding head 10 onopposite sides of the drive roll 31 and each cooperates with the driveroll 31 to provide one of the lancing stations 24. With thisarrangement, two lancing stations 24 are provided with only threelancing rolls since the single drive lancing roll 31 functions as partof each of the lancing stations.

Each of the lancing rolls 31, 32, and 33 is formed with upper lancingteeth 34 and lower lancing teeth 36 separated by a space 37. The lancingteeth intermesh so that the idler rolls 32 and 33 are driven by thedrive roll 31 at the same rotational velocity as the drive roll 31 butin an opposite direction. The lancing teeth lance opposite sides of thestrip 16a as illustrated in FIG. 40 so that the strip has cuts 41 and 42extending in from the adjacent opposite edges, respectively, andterminating at spaced locations to provide a central uncut portion 43.Between each cut 41 and 42 is a separate fin 44 which is joined to theuncut section 43 at its inner end.

From the lancing station 24 the strips 16a and 17a move to therespective first fonning stations 26 one of which is illustrated in FIG.5. Located at each first forming station 26 is a driven roller 40 and anidler roller 42 which are respectively joumaled for rotation aboutspaced and parallel axes 43 and 45. The driven roller 40 is formed witha shallow annular groove 46 and cylindrical surfaces 47 and 48 on eitherside thereof. The total height of the space 46 and surfaces 47 and 48 isat least as great as the lateral width of the lanced strips so that thefins 44 are not damaged as the lanced strips engage the periphery of theroll 40.

The idler roll 42 has a lateral width or height equal to the desiredwidth of the U-shaped strip 16b and 17b. This roll projects into thegroove 46 and cooperates with the side walls 49 to deform the strip to aU-shape in which the strip has a base 51 and substantially parallel legs52 and 53 extending from the opposite edges of the base 51. The twostrips 16a and 17a engage their respective driven rollers 40 at atangential location spaced from the associated idler rollers 42 and arecarried along the drive rollers until they engage the idler rollers 42.At this location where the idler roller 42 projects into the groove 46,the respective strips are deformed to a U-shaped condition.

From the first forming station each of the strips passes to a secondforming or hemming station having a mechanism as illustrated in FlGS. 6and 60. Located at each hemming station 27 is a hemming assembly 56which provides three interconnected forming rolls 57, 58, and 59 whichcooperate with an idler roll 61 illustrated in FIG. 6a. The hemmingassembly 56 is a separate assembly which may be installed in the winding head or removed therefrom as a unit. This greatly facilitates theservicing of the machine since a separate hemming assembly 56 can beserviced and adjusted while the machine operates with another hemmingassembly in position.

The hemming assembly includes an upper housing member 62 and a lowerhousing member 63 which are bolted together and are in turn bolted tothe winding head by bolts 64. Journaled on the lower frame 63 in anantifriction bearing assembly 66 is an input drive shaft 67 providedwith an internal spline adapted to fit over and be drivingly connectedto a drive shaft 68. The upper end of the shaft 67 is provided with amiter gear 69 which meshes with a miter gear 71 which is journaled forrotation about a horizontal axis 72. The miter gear 71 is provided witha support shaft 73 joumaled in bearings 74 and 76 in the lower housing63. The roller 57 is removably mounted on the forward face of the mitergear 71 by bolts 77.

The upper end of the miter gear 71 also meshes with a miter gear ring 78which together with the base roll 58 and a second miter gear ring 79form a ring assembly which is mounted on the outer race 81 of anantifriction bearing assembly 82. The bearing assembly 82 is in turnsupported by a pin 83 mounted between the two housings 62 and 63 on avertical axis intersecting the axis 72. The miter gear ring 79 mesheswith a miter gear 84 which is similar to the gear 71 and which supportsthe upper roll 59. Here again the miter gear 84 is provided with a shaftsection 86 joumaled in bearings 87 and 88 for rotation about ahorizontal axis 89 which intersects the axis of the pin 83 and isparallel to the axis 72 and vertically spaced therefrom.

The three rolls 57, 58, and 59 all have substantially the same diameterand rotate at the same velocity to minimize any tendency for skidding tooccur when the strip is engaged. With this gear drive the adjacentsurfaces of the three rolls move in the same direction. The variouselements are proportioned so that the U-shaped strip 16b and 17b engagesthe base roll 58 ahead of the two rolls 57 and 59. As the strip iscarried into the throat as illustrated in FIG. 6a, the two legs of thestrip are deformed to provide a hem portion 91 extending inwardly fromthe edge of the base 51. The inner faces 92 of the two rolls 57 and 59are formed with a shallow conical shape and cooperate with the conicalside faces 90 of the idler roll 61 to insure that the fins 44 aresubstantially coplanar with their adjacent fins and to insure that thetwo legs diverge slightly.

The roll 61 is joumaled for free rotation in response to engagement withthe associated strip on a mounting spindle (not illustrated for purposesof simplification) which permits both vertical and radial adjustment ofits position. With such adjustment the exact desired relativepositioning of the side faces 90 with respect to the associated innerfaces 92 can be obtained. Radial adjustment, because of the conicalshape of the faces 90 and 92, provides adjustment of the total spacingtherebetween and vertical adjustment permits equalizing of the spacing.

The hemmed strip 16c or 17c then passes around the associated inclinedroll 28 which is positioned so that the respective strips are inclinedupwardly toward the tube 12 at an angle substantially equal to the helixangle of winding. As the strips are wound on the tube the outer wall ofthe hem 91 is pulled tighter than the inner wall because of thedifference in diameter, so the fins 44 are pulled inward and becomesubstantially parallel.

FIG. 7 illustrates one form of a final heat exchanger tube whichconsists of the tube 12 and the two strips 160 and 170 which are woundon the tube with a double helix. The helix angle is such that the leadof the helix of each strip is equal to twice the width of the base 51 ofeach strip and the base 51 of the strip 16c is directly opposite thebase 51 of the strip 170. With such a helix angle the bases of the twostrips engage opposite sides of the tube. In some instances where aspacing is desired between the two bases, the helix angle may be furtherincreased by increasing the rate of feed of the tube during winding.This produces a space between the adjacent bases 51. In other instanceswhere a wide space is desired, the winding head can be supplied with asingle strip without changing the rate of tube feeding and a space willoccur between the base of the strip along one turn and the adjacent turnwhich is equal to the width of the base which would otherwise beprovided by the second strip.

FIG. 7a illustrates a modified form of tube wherein two strips of hemmedfoil 16c and 170' are again wound on the tube 12 with a double helix.However, the base 51' of the strip 17c is wider than the base 51' of thestrip 16c and the fins 44' of the strip 170' are correspondinglyshorter. In this form the stock for the two strips has the same initialwidth even though they are formed in different proportions. The twostrips, however, do not have to have the same width when the stripshapes are not identical.

Reference should now be made to FIGS. 2 and 3 which illustrate the basicdrive for the various elements of the winding head 10. The entirewinding head 10 is supported on a tube 101 which is rotated about thecentral axis 11 by a drive system as illustrated in my prior US. Pat.No. 3,160,129. The drive in the illustrated embodiment causes clockwiserotation of the winding head as viewed in FIG. 2 in response to rotationof the drive tube 101.

Extending up through the drive tube 101 is an inner drive tube or torquetube 102. Here again this tube is driven by the lower drive unit in aclockwise direction as viewed in FIG. 2, but at a slower velocity thanthe winding head 10. A nonrotating guide tube supports the guide 13. Thedrive tube 102 is formed with an internal spline 103 which engages aspline on a shaft 104journaled in bearings 106 and 107, so that theshaft 104 is driven by the tube 102. The drive lancing roll 31 iscarried by a shaft 104 and rotates therewith. Also mounted on the shaft104 is a center drive gear 108.

Because the rate of rotation of the center drive tube 102 is slower thanthe rate of rotation of the winding head 10, the gear 108 and thelancing roll 31 rotate in an anticlockwise direction as indicated by thearrow 109 with respect to the winding head even though the absoluterotation of the gear 108 and lancing roll 31 is in a clockwisedirection. For purposes of discussion the following description of thewinding head drive refers to the rotation of the various elements of thewinding head with respect to the main winding head frame as if thewinding head frame were stationary and the various components of thewinding head were rotated in a stationary winding head frame. It must beunderstood, however, that in fact the winding head itself is rotatingand that the absolute rotational movement of the components is notnecessarily in the directions set forth.

Because the gear 108 and the lancing roll 31 rotate about the centralaxis 1 1 the support bearings for these elements are not subjected toany substantial centrifugal force. Mounted in the frame assembly 111 ofthe winding head 10 is a pivot assembly 1 12 for each of the idlerlancing rolls 32 and 33. This pivot assembly includes a pivot pin 113supported by spaced bushings 114 and 116. During the operation of themachine the pivot pin 1 13 is clamped in its adjusted position, but itcan be rotated with respect to the frame 1 1 1 for adjustment of theradial spacing of the associated idler lancing roll 32 or 33. The pin113 is provided with an eccentric cylindrical surface 117 which supportsthe inner race of a bearing assembly 118. Mounted on the external raceof the bearing assembly 118 is the idler roll 32. As the drive lancingroll 31 is rotated by the drive, the idler roll 32 is caused to rotateabout the axis of the eccentric portion 117. Radial adjustment of theidler roll 32 is provided by loosening a clamp nut 1 19 to release theclamping force of a clamp washer 121 to permit the, pivot pin 113 to berotated. When the proper position is achieved, the nut 119 is tightenedcausing the clamp washer 121 to be pulled up against the lower side ofthe bushing 116 and causing it to be axially gripped by a spacer 122which extends between a flange 123 and the upper side of the bushing 116. The adjustment of the pivot pin 113 is easily accomplished by theuse of a wrench on wrenching flats formed at 124 on the pin.

lt should be recognized that this adjustment and mounting wherein thepivot pin 1 13 is not joumaled for rotation with respect to the frame 111 permits the use of smaller bearings because the mass which must besupported by the bearings 118 is the roll 32 and the mounting partsadjacent thereto. Consequently, the only centrifugal forces which mustbe supported by the bearings 118 as the winding head rotates are theforces resulting from the relatively small mass of the lancing roll 32and adjacent rotating parts. Of course, these bearings must also sustainthe lancing loads.

Meshing with the central gear 108 are a pair of opposite gears 126associated with each of the hemming assemblies. These gears are locatedat diametrically opposite locations with respect to the central axis 11and both rotate in a clockwise direction with respect to the frameassembly 111. FIG. 3 is a broken section so only one of these gearsappears in the section.

The gear 126 is mounted on the shaft 68 which is in turn joumaled inbearings 127 and 128. The upper end of the shaft is provided with aspline which fits into the drive shaft 67 of the associated hemmingassembly 56. The clockwise rotation of the gear 126 is thereforetransmitted to the first miter gear 69 illustrated in FIG. 6 as movementindicated in the direction of the arrow 129. This causes movement of thelower portion of the miter gear 71 in a direction out of the plane ofFIG. 6 and movement of the upper portion in the opposite direction orinto the plane of FIG. 6 which is the desired direction of rotation forthe roll 57. Because of the interconnection of the three rolls discussedabove, the movement of the adjacent portions at the hemming station isall in the same direction.

Each of the gears 126 meshes with an associated gear 131 which powersthe roll 41 on a first forming station. Because of the clockwiserotation of the gears 126, each of the gears 131 rotates in ananticlockwise direction with respect to the winding head frame assembly111. The gears 131 are connected through a shaft 132 to the drive roll40 of the associated first forming station. This produces rotation ofthe drive rolls 40 in the correct direction with respect to the head.The drive shaft 132 is also provided with a smaller diameter gear 133which also rotates in an anticlockwise direction and meshes with anidler gear 134 causing it to rotate in a clockwise direction at avelocity substantially slower than the velocity of the shaft 132 due tothe difference in diameter of the two gears. The gear 134 meshes with aring gear 136 which is mounted on the stock support table 14 to causerotation of the stock support table 14 in a clockwise direction withrespect to the winding head frame assembly 11 1.

Preferably, the two first forming stations 26 are both provided with agear 133 even though only one gear 134 is provided. With thisarrangement the structure of the elements of the first forming stationsare identical and interchangeable. Further, such an arrangement improvesdynamic balance of the machine. The only nonsymmetry in the winding headis the single gear 134 which is not duplicated on the opposite side ofthe winding head. However, a weight 135 of identical mass is locatedopposite the gear 134 in the same physical location with respect to thecentral axis so complete dynamic balancing of the machine is achieved.Such dynamic balancing is, of course, important since the winding headrotates with a relatively high velocity and imbalance would causeextreme loads on the various bearing support systems.

Because the various gear elements are arranged so that proper rotationaldirection is obtained without need of idler gears or the like to reversedirections, a very simple gear train is provided even though the windinghead is arranged to simultaneously process two strips of foil. Thecenter gear 108 because of its central location, can be used to driveboth of the gears 126. Similarly, the gears 126 for each of the hemmingstations are used to drive the gears 131 associated with the two firstforming stations. The size of the gears are selective with respect tothe size of the various rollers so that the strips are tensioned as theypass from one operation to the next and are actually stretched slightlyat the time they are wrapped around the tube 12. Consequently, theinternal stress in each strip insures that each of the strips tightlyadheres to the tube and a good heat exchange contact is provided. Whenthe foil strips are formed of the same material as the tube these stripsare directly wound onto the tube. However, when the tubing and the foilare formed of two difi'erent materials, such as aluminum and a ferrousmetal, it is preferable to coat the tubing with a dielectric adhesivelayer at 130 to prevent galvanic action between the two dissimilarmetals. Such dielectric material is pumped into the tube and coats thetube 12 as it passes therethrough. Such a layer is not required,however, for its adhesive function, although it tends to provide a bondbetween the tube and the foil strips.

Reference should not be made to FIGS. 8 through 11 which progressivelyillustrate the manner in which the stock of interleaved strips ofmaterial is fed into the winding head. in FIG. 8 a coil of stock 141 isillustrated on the stock support table 14 in a position around thewinding head 10 and coaxial with the central axis 11. This coil of stockconsists of the two strips 16 and 17 wound in an interleaved doublespiral. The strip 16 is illustrated in solid line and the strip 17 indotted line for purposes of illustration. The strip 16 is threaded intothe winding head 10 around the roller 18 and enters the head at 142. Thestrip 17 however extends around the winding head over its associatedroller 18 and enters the winding head at 143, a location diametricallyspaced from the location 142.

Initially, the coil stock is spaced from the winding head 10 and has athickness indicated at A. As the machine commences to wrap the tubing,the coil of stock 141 carried by the table 14 rotates in a clockwisedirection at the same time the winding head rotates in a clockwisedirection at a slower velocity. The two strips 16 and 17 unwind from theinner diameter of the coil 141 at a faster rate than the stock feedsinto the winding head. This causes some of the stock to build up aroundthe winding head and form an inner coil at B where it is guided by therollers 18 carried by the winding head. The buildup of an inner coilcontinues until approximately one-half of the stock has been removedfrom the inside of the coil 141. At this point in the cycle of operationillustrated in FIG. 10, the thickness of the inner coil B is at amaximum thickness.

Continued operation of the machine approaching the condition of FIG. 11wherein the outer coil 141 is almost exhausted results in the decreasingthickness of the inner coil as illustrated in FIG. 11. Since the twostrips are of substantially the same length, both strips are exhaustedat about the same time. Of course, the inner of the two interleavedstrips is shorter than the outer strip because it is wound on a spiralof smaller radius. However, the difference in length does not produceany problem since the manner in which the strips unwind from the outercoil and rewind on the inner coil accommodates the difference in lengthas illustrated by the progressive separation of the two strips extendingfrom the outer coil to the inner coil. So long as the difference inlength of the zone of interfacial contact between the two strips doesnot exceed the peripheral length of the outermost layer of suchinterfacial contact, the free portion of the outer strip 17 will notreach the free portion of the inner strip 16 and the two strips willfeed properly. The manner in which the coils unwind and form an innercoil is described in more detail in my US. Pat. No. 3,134,166. Theprincipal difference however, is that the two coils are not of the samelength and it is necessary to accommodate this difference in length byarranging the mechanism so that the two strips can separate as they movefrom the outer supply or stock coil to the inner coil around the head.

With a machine in accordance with the present invention the linealoutput of wound tube is doubled when compared to a prior single stripmachine. The double wound tubing because of its greater helix angletends to increase the turbulence of air flowing over the fins andthereby improves the heat exchange capacity of the tube. Further, thelayer of the dielectric coating between the strips and tubes is moreuniform since the lateral forces of the strips are balanced and the tube12 is not pulled over against the guide 13. Further, the double helixwinding of the tube increases the helix angle of the stress zones whichthe strips produce in the base tube. Consequently, the tube is not assusceptible to rupture when it is bent for installation in theassociated equipment.

The illustrated embodiment of the machine obtains such increased outputwith a simplified gear drive system. The machine is also arranged sothat it may be easily serviced. For example, the idler lancing rolls canbe easily removed and replaced and the hemming assembly can be easilyremoved and replaced. Since the load on the bearing of the lancing rollsis the greatest load involved in the fonning operation, the centrallocation of the lancing stations close to the central axis 11 reducesthe load on the bearings by reducing the centrifugal force. Further, thetwo lancing operations are accomplished with only three lancing rolls.The use of hemming rolls located at right angles to each other furthersimplifies the structure of the machine and the drive of the variousrolls.

Although preferred embodiments of this invention are illustrated, it isto be understood that various modifications and rearrangements of partsmay be resorted to without departing from the scope of the inventiondisclosed and claimed herein.

What is claimed is:

l. A machine for winding strip material around a tube or the likecomprising:

a winding head rotatable about an axially disposed passage therein,

means for advancing said tube at a governed rate through said axialpassage,

a coil support around said winding head supporting and rotating a coilconsisting of a plurality of long strips wound in interleaved spirals,

said winding head including feed means operable to separately andsimultaneously feed said strips from the interior of said coil, fomiingmeans operable between said feed and winding means for forming each ofsaid strips into a cross section having a base section and at least oneleg section, and means to simultaneously wind the formed strips on thetube in a multiple helical form.

2. A machine as set forth in claim 1 wherein the rate said tube isadvanced through said axial passage is at a rate timed with respect tothe winding head rotation to wind said formed strips as a multiple helixin which the base sections of adjacent turns touch.

3. A machine as set forth in claim 2 wherein the forming means formseach of said strips into substantially U-shaped cross section having abase section and two spaced leg sections.

4. A machine as set forth in claim 3 including lancing means forseparately and simultaneously lancing the edge portions of said stripsfed from said coil,

and said forming means includes means for separately and simultaneouslyforming said lanced strips into said U-shape with said lanced portionsforming said legs, and hemming means operable to separately andsimultaneously form a hem on each of said leg sections adjacent saidbase section.

5. A machine as set forth in claim 1 wherein the means for feeding,forming and winding of each of said strips are generally located onopposite sides with respect to said axis of said winding head.

6. A machine for winding strip material around a tube or the likecomprising:

a winding head rotatable about an axially and vertically disposedpassage therein,

means for advancing said tube at a governed rate vertically through saidaxial passage,

a coil support around said winding head supporting and rotating a coilconsisting of two strips wound in interleaved spirals,

feed means including a pair of lancing stations symmetrically positionedwith respect to said central axis for separately lancing a strip,

a pair of first forming stations symmetrically positioned with respectto said central axis for initially {owning a lanced strip,

7. A machine as set forth in claim 6 wherein the rate said tube isadvanced through said axial passage is at a rate timed with respect tothe winding head rotation to wind said formed strips as multiple helixin which the base sections of adjacent turns touch.

8. A machine as set forth in claim 7 wherein the formed stripstangentially engage diametrically opposite sides of said tube duringwinding of said strips onto said tube.

I I ll l

1. A machine for winding strip material around a tube or the likecomprising: a winding head rotatable about an axially disposed passagetherein, means for advancing said tube at a governed rate through saidaxial passage, a coil support around said winding head supporting androtating a coil consisting of a plurality of long strips wound ininterleaved spirals, said winding head including feed means operable toseparately and simultaneously feed said strips from the interior of saidcoil, forming means operable between said feed and winding means forforming each of said strips into a cross section having a base sectionand at least one leg section, and means to simultaneously wind theformed strips on the tube in a multiple helical form.
 2. A machine asset forth in claim 1 wherein the rate said tube is advanced through saidaxial passage is at a rate timed with respect to the winding headrotation to wind said formed strips as a multiple helix in which thebase sections of adjacent turns touch.
 3. A machine as set forth inclaim 2 wherein the forming means forms each of said strips intosubstantially U-shaped cross section having a base section and twospaced leg sections.
 4. A machine as set forth in claim 3 includinglancing means for separately and simultaneously lancing the edgeportions of said strips fed from said coil, and said forming meansincludes means for separately and simultaneously forming said lancedstrips into said U-shape with said lanced portions forming said legs,and hemming means operable to separately and simultaneously form a hemon each of said leg sections adjacent said base section.
 5. A machine asset forth in claim 1 wherein the means for feeding, forming and windingof each of said strips are generally located on opposite sides withrespect to said axis of said winding head.
 6. A machine for windingstrip material around a tube or the like comprising: a winding headrotatable about an axially and vertically disposed passage therein,means for advancing said tube at a governed rate vertically through saidaxial passage, a coil support around said winding head supporting androtating a coil consisting of two strips wound in interleaved spirals,feed means including a pair of lancing stations symmetrically positionedwith respect to said central axis for separately lancing a strip, a pairof first forming stations symmetrically positioned with respect to saidcentral axis for initially forming a lanced strip, and a pair of secondforming stations symmetrically positioned with respect to said centralaxis for further formings of each strip, said lancing stations beingprovided by a drive roll journalled for rotation around said centralaxis and two cooperating idler rolls journalled for rotation about axeson opposite sides of said central axis, each idler roll cooperating withsaid drive roll to provide a lancing station on opposite sides of saiddrive roll.
 7. A machine as set forth in claim 6 wherein the rate saidtube is advanced through said axial passage is at a rate timed withrespect to the winding head rotation to wind said formed strips asmultiple helix in which the base sections of adjacent turns touch.
 8. Amachine as set forth in claim 7 wherein the formed strips tangentiallyengage diametrically opposite sides of said tube during winding of saidstrips onto said tube.